Rotary vacuum pump of the liquid-ring type



1968 E. SCHRODER 3,366,314

ROTARY VACUUM PUMP OF THE LIQUID-RING TYPE Filed Oct. 11, 1965 United States Patent ()fifice 3,365,314- Patented Jan. 30, 1968 3,366,314 ROTARY VACUUM PUMP OF THE LIQUID-RING TYPE Erich Schriider, Mulheirn (Ruhr), Germany, assiguor to Siemens-Schuckertwerlre Aktiengesellschaft, Berlin and Erlangen, Germany, a corporation of Germany Filed Oct. 11, 1965, Ser. No. 494,807 Claims priority, appiication Germany, Apr. 28, 1965, S 96,807 6 Claims. (Cl. 230-79) ABSTRACT OF THE DISCLOSURE Rotary vacuum pump of the liquid-ring type, comprising a stationary structure forming a housing and having a suction port and a pressure port, a multi-blade rotor rotatable in the housing and forming peripherally sequential cells for entraining gas through the suction port and passing it compressed through the suction port, the structure having a number of openings through which the cells communicate with the outside of the structure, the openings being situated close to the pressure port at respective localities ahead of the pressure port relative to the direction of rotor rotation, the peripherally sequential cells, respectively, defining with the structure a compression terminal space adapted to sweep past the openings successively and being variable in volume in accordance with suction pressure applied through the openings, at single flexible check-valve plate common to the openings and sealingly engageable with the structure for jointly closing the openings under external pressure, the valve plate being displaceably mounted on the structure for successively closing a varying number of the openings progressively in the direction of rotor rotation by external pressure and for successively opening a varying number of the openings to thereby relieve internal overpressure.

My invention relates to rotary gas pumps for producing or maintaining a vacuum under changing pressure conditions. In a more particular aspect, the invention concerns rotary vacuum pumps of the liquid-ring type, also called liquid-piston type.

Pumps of this type require a compression terminal space of more or less volume depending upon the compression ratio. This terminal space is bordered by the control discs or surfaces of the pump housing, by the ring-shaped body of liquid rotating in the housing, by the hub of the multi-blade rotor, and by the position of the particular rotor blade cell in which the ultimate pressure, usually atmospheric pressure, is attained. It is known to make this terminal space variable by providing the control plate or housing of the pump with a number of bores which are located just ahead of the pressure outlet port and are closed on the back pressure or check-valve principle, the outer openings of the bores being located in liquid, such as oil or water. By virtue of these checkvalve bores, gas can escape from the interior of the pump into the liquid-filled surrounding space if the pressure in the pump becomes excessive. On the other hand, the check-valve bores prevent expelled gas from passing back into the working space of the pump if the latter is under lower pressure than obtains in the environment space of the pump.

The above-mentioned operating conditions of the conventional liquid-ring pumps for vacuum operation, as well as the objects and features of the present invention, will be explained in the following with references to the accompanying drawings, in which:

FIG. 1 shows a lateral view of a liquid-ring pump according to the invention, this view, however, being identical with the external appearance of a known pump.

FIG. 2 shows a section through the check-valve portion of a pump according to the prior art.

FIG. 3 shows a section along the line III-III in FIG. 4; and

FIG. 4 is a partial lateral view of a pump according to the invention, this pump being otherwise in accordance with FIG. 1.

Referring to FIG. 1, the housing of the illustrated pump is denoted by P and the multi-blade rotor by L, the blades of the rotor being represented by broken lines. The rotor is mounted in eccentric relation to the pump housing. It should be understood, however, that in some known pumps the rotor is mounted in concentric relation to the housing but the latter is given an elliptical interior cross section. In either case, the housing is partially filled with liquid, such as water or oil, so that, during rotation of the rotor, the liquid is caused by centrifugal force to form a rotating ring along the inner periphery of the housing. This ring of liquid enters to a larger or smaller extent into the respective cells formed between each two adjacent rotor blades. During rotation of the rotor, the eccentricity of the liquid ring causes the volume of the gas chamber within each cell to change continuously, thus compressing the gas which enters into the cell spaces through an inlet port. In the illustrated pump, the inlet port is constituted by a relatively long suction slot 4 which communicates with the vessel or other enclosed space to be evacuated. The gas, progressively compressed in the cell chambers as the cells travel clockwise with the rotor, leaves the pump through an outlet port or pressure slot 2 which is considerably smaller than the suction slot 4. Located just ahead of the pressure slot 2 are a number of bores 3 which, as explained above, permit the escape of gas from the working space of the rotor when the pressure in this space is too high, and also permit a flow of gas in the opposite direction if the pressure in the rotor is too low.

As shown in FIG. 2, the bores 3 are normally closed by valve balls 5 which are individually movable in a valve cage 6 and which open and close the respective bores in accordance with the pressure conditions just mentioned.

It is an object of my invention to improve and considerably simplify pumps operating generally on the principle of liquid-ring principle described above.

Another object of my invention is to aiford controlling or adjusting the displacement of the check-valve means in a liquid-ring pump in order to improve its adaptability to particular operating conditions.

Still another object of the invention is to devise a liquidring pump which is less sensitive to detrimental effects of impurities and exhibits a considerably smaller amount of wear than those heretofore available.

According to my invention, and referring to a liquidring pump with a number of bores located closely ahead of the outlet pressure port, I provide a single flexible check-valve plate common to the bores for jointly closing them under external pressure, the valve plate being displaceably mounted on the housing structure or control plate of the pump for movement away from the bores to thereby relieve internal overpressure.

According to another, preferred feature of my invention, the check-valve plate common to all of the abovementioned bores is held in proper position by guide members which are inserted into the control plate or housing structure of the pump and permit limiting or adjusting the displacement of the valve plate.

The foregoing, and further features of my invention, said features being set forth with particularity in the claims annexed hereto, will be apparent from the em- 3 bodiment exemplified by FIGS. 3 and 4 of the drawing and described presently.

As shown in both illustrations, the portion of the control plate 1 which forms part of the housing structure and contains the bores 3 is completely covered by a valve plate 7. The upper and lower end of the plate 7 are provided with an elongated opening 9 and round opening 9 respectively, the openings are traversed by respective guide members 8 consisted in this embodiment by respective bolts whose threaded portion 8a is screwed into the control plate 1 and which have a shoulder portion 8b passing through the respective openings 9 and 9 of the valve plate 7. The head 30 of each member 8 has a larger diameter than the shoulder portion 8b and forms a stop to limit the displacement of the valve plate 7 away from the control plate 1.

The valve plate 7 consists of sheet metal and is relatively thin so as to be flexibly bendable. As a result, the valve plate 7 is placed snugly and tightly against the lateral side of the control disc 1 in the region of the bores 3 when external pressure is applied to the valve plate. The plate 7 may consist of metal, for example stainless steel, or some other material resistant to corrosion.

According to another feature of my invention, however, the valve plate 7 is made of a synthetic plastic of virtually no adherence to impurities such as limestone or other incrustation as may become deposited from the water, assuming that the pump is operated with water. Particularly well suitable for the purpose of the invention is the use of polytetrafiuoroethylene as material for the valve plate 7, this material being available under the tradename Teflon in the form of flexible sheets. Aside from its excellent precipitation-preventing properties, this material is chemically stable and has an extremely high resistance to Wear.

A liquid-ring pump according to the invention is particularly advantageous because it is much simpler and hence more reliable than the above-mentioned known pumps equipped with ball-type check valves. Besides, the valve plate in a pump according to the invention has a much longer useful life because of the reduced wear in comparison with the ball-shaped valve bodies of the know pumps. 1

Another advantage of pumps according to the invention is the possibility of increasing the flow cross section of the valve openings. This is due to the fact that the amount of material which must necessarily remain between adjacent bores can be reduced in comparison with the material required between the individual bores of balltype valve bodies.

Relative to the above-mentioned state of the art, ref- .erence may be had to the booklet entitled Design and Range of Application of ELMO Vacuum Pumps, published by Siemens-Schuckertwerke A.G., Berlin and Erlangen, Germany (Order No. 474.1/245).

Upon a study of this disclosure it will be obvious to those skilled in the art that my invention is amenable to a variety of modifications and may be given embodiments other than particularly illustrated and described herein without departing from the essential features of my invention and within the scope of the claims annexed hereto.

I claim:

1. A rotary vacuum pump of the liquid-ring type, comprising a stationary structure forming a housing and having a suction port and a pressure port, a multi-blade rotor rotatable in said housing and forming peripherally sequential cells for entraining gas through said suction port and passing it compressed through said pressure port, said structure having a number of openings through which said chambers communicate with the outside of said structure, said openings being situated close to said pressure port at respective localities ahead of said pressure port relative to the direction of rotor rotation, said peripherally sequential cells, respectively, defining with said structure a compression terminal space adapted to sweep past said openings successively and being variable in volume in accordance with suction pressure applied through said openings a single flexible check-valve plate common to said openings and sealingly engageable with said structure for jointly closing said openings under external pressure, said valve plate being displaceably mounted on said structure for successively closing a varying number of said openings progressively in the direction of rotor rotation by external pressure and for successively opening a varying number of said openings to thereby relieve internal overpressure.

2. A rotary vacuum pump according to claim 1, comprising guide means mounted on said structure and in engagement with said valve plate for securing said valve plate in proper position, said guide means forming a stop for limiting the valve-opening displacement of said valve plate.

3. In a rotary vacuum pump according to claim 1, said valve plate being formed of sheet metal consisting of corrosion resistant material.

4. In a rotary vacuum pump according to claim 1, said valve plate being formed of stainless steel sheet material.

5. In a rotary vacuum pump according to claim 1, said valve plate being formed of synthetic plastic sheet material.

6. In a rotary vacuum pump according to claim 1, said valve plate being formed of polytetrafluoroethylene.

References Cited UNITED STATES PATENTS 1,180,613 4/1916 Siemen 23079 2,838,072 6/1958 Stumrn. 3,102,455 9/1963 Breitenstein. 3,177,781 4/ 1965 Macfarlane. 3,185,388 5/1965 Siman et al. 230228 FOREIGN PATENTS 525,761 9/ 1940 Great Britain.

HENRY F. RADUAZO, Primary Examiner. 

